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Multitalented giant clams keep corals reefs healthy

IT’S time they came out of their shells. It seems the world’s largest molluscs, the giant clams of the Indo-Pacific coral reefs, have been doing a huge amount of good work we knew little about. These sea creatures turn out to be multitasking ecosystem engineers. They are reef builders and shapers, food factories, shelters, reservoirs of algae and water filters – all in one.

Giant clams have been around for about 38 million years. The largest ones can grow to 1.2 metres long and weigh more than 200 kilograms. But their role in the ecosystem is poorly understood, says Peter Todd, a marine ecologist at the National University of Singapore. Todd’s team investigated the role the molluscs play in their surroundings to try and shed some light.

They found that the 13 giant clam species are food factories for coral reef inhabitants, nurseries and refuges for young fish, and sites for adults laying eggs (Biological Conservation, doi.org/xrc). They also make carbonate shell material, which helps build the reef structure.

“They are a vital indicator species of coral reef health and their ecological contributions are innumerable,” says Deepak Apte of the Bombay Natural History Society in India. But these benefits are likely to continue only if giant clam populations are healthy. The team hopes their work will reinforce the case for conserving the molluscs, which are currently vulnerable.

This article appeared in print under the headline “Giant clams are multitalented coral-reef support systems”